The work outlined in this proposal relies heavily on labeling cells with surface and internal markers linked to fluorescently-labeled antibodies for analysis or sorting. The Fluorescent Activated Cell Sorting Core Facility (FACS) will continue to support Program Project investigators by providing cell sorting, FACS analysis, data interpretation, database creation and storage, and experimental design services. The Core is located within a newly constructed, interdepartmental laboratory within the University of Massachusetts Medical School. This Core enhances the productivity of the proposed research by: a) providing state-of-the-art equipment and services not available in individual laboratories; b) allowing investigators to focus on their particular projects without the need to develop and staff their own flow cytometry/cell sorting facility; c) encouraging interactions between investigators who share the resources of this core facility; and d) providing flow cytometry education in theory and applications as well as interpretation of data. Services are provided in the following areas: 1. Flow Cytometry Analysis: This facility is equipped with three dual laser FACSCalibur analyzers; a 10- color, 4-laser LSR II high-speed analyzer; and a 12-color, 4-laser LSR II high-speed analyzer. 2. High Speed Cell Sorting: To enable researchers to enumerate and isolate unique and potentially rare cell populations, the FACS Core is equipped with three multi-laser cell sorters including a 3-laser, 8- color Becton-Dickinson FACS Vantage with DIVA high speed electronics; a newly developed 11- color, 3-laser FACS Vantage SE DIVA/MDO with digital processing and fiber optic detectors; and a 3- laser, 9-color DakoCytomation MoFlo MLS. The FACS Core facility thus serves as a pivotal point for exchange of Flow Cytometry science, education, service and technology amongst Program Project investigators.